Stimulus overselectivity, also known as restricted stimulus control, is a widely acknowledged problem in the education of individuals with developmental disabilities. Overselectivity refers to learning that is atypically limited with respect to range, breadth, or number of stimuli or stimulus features. This project will continue ongoing studies of variables that affect overselectivity and the development of stimulus control by multiple or multi-element stimuli. While no generally applicable procedures for solving the problem have yet emerged, our progress thus far has set the stage for such an effort. Research during the current grant period provides compelling evidence that overselectivity (1) is open to manipulation by reinforcement contingencies, (2) may be directly related to deficiencies in observing behavior, and (3) can be greatly reduced by interventions that control observing behavior. The project contributes to the overall program project effort by developing generally effective procedures for broadening stimulus control. The goals of the proposed research are: (1) To investigate environmental variables that may affect the behavioral aspects of stimulus overselectivity, including reinforcement variables that have been little studied in past research; (2) to develop effective remedial procedures that reduce or eliminate overselectivity. Approaches include stimulus control shaping of effective observing, manipulating stimulus context to promote more effective observing, manipulating stimulus context to promote more effective observing, and teaching participants to make explicit responses that guide effective observing, and teaching participants to make explicit responses that guide effective observing. Results of these studies are expected to advance not only scientific understanding of overselectivity, but also to establish methodology that will be useful in clinical and educational remediation efforts.